Up to recently the quality of products from tool steels produced by conventional metallurgical methods was improved by way of complicating their chemical composition, which involved considerable difficulties caused by a sharp deterioration in the ductility of cast metal and a decrease in an ingot-to-product yield.
The use of improved production techniques and processes (electroslag remelting process, the use of large ingots and high-temperature treatment prior to deformation in presses, hot extrusion of ingots) has made it possible to somewhat increase the ingot-to-product yield and to upgrade its quality in a stage process of tool steels but has not allowed for the solution of the problem as a whole.
One of the ways of solving said problem is to produce products from tool steels by the method of powder metallurgy. Such steels are distinguished from the cast ones by the absence of chemical structural non-uniformity, by the size and character of distribution of carbides, which substantially improves the ductility of the steel, increases the ingot-to-product yield of metal and the operation characteristics of products.
Known in the art is a method of making products from stainless steel powders (see, for instance, USSR Inventor's Certificate No. 418,271, published on June 9, 1977), comprising charging a powder into a capsule, heating, sealing and deformation of the capsule. The capsule with the powder contained therein is heated up to the deformation temperature in the atmosphere of hydrogen and held at this temperature for 1 to 6 hours. Then the capsule is sealed in a furnace.
The described method makes it possible to reduce the oxides on the metal particles and to obtain metal of dense structure. However the necessity of using costly equipment in special furnaces with the atmosphere of highly-purified hydrogen the maintainance of which under the conditions of an increased explosion hazard requires special measures for ensuring safe operation and considerably impedes the industrial implicability.
Known in the art is a method of making products from high-speed steel (see Inventor's Certificate No. 417,246, published on June 9, 1972), comprising charging a powder into a capsule, pumping off air therefrom, sealing, heating and deformation of the capsule. This being the case, the capsule with the powder contained therein is heated up to a temperature of 1050.degree. to 1150.degree. C. and then extruded at a degree of deformation of 70 to 90%.
The method is comparatively cheap and simple. However, the presence of oxides in the deformed metal reduces its strength and operation characteristics. This takes place because, as a result of heating the capsule for deformation, reversible redox processes occur therein, which processes are due to the reduction of the oxides by carbon of the powder of the steel and formation of carbon oxide and carbon dioxide therewith. The carbon dioxide is an active oxidizer of metal.
The object of the invention is to provide a method of making products from powders of tool steels, wherein the production techniques and conditions make it possible to substantially reduce the content of oxides in the deformed metal and thereby to upgrade its strength and operation characteristics.